1. Field of the Invention
The present invention relates to the construction of a metal punch, and, more particularly, to the construction of a two-piece metal punch.
2. Description of the Related Art
A metal punch is traditionally made as a one-piece construction. The one-piece construction is typically made of a single piece of carbide. The punch is produced from a carbide preform whereby the rough shape of the punch is established in a pre-sintered state. The head, thickness dimensions, shank diameter (if of a shanked design), and the punch contour are finish ground. This method of creating a one-piece punch, however, is expensive and time-consuming. While this structure has the advantages of rigidity and strength, the material and labor necessary to produce a one-piece carbide punch cause such punches to be expensive.
A two-piece punch construction is an alternative to a one-piece construction. A common two-piece punch construction, however, only overcomes one problematic aspect of a one-piece construction. The common two-piece punch construction, while less time-consuming and expensive to make, is not as strong and rigid as the one-piece punch construction. In a two-piece punch construction, the punch body is made in the form of a xe2x80x9cstickxe2x80x9d by using wire electrical discharge machining (WEDM) of a rectangular stock block of carbide. Alternatively, the punch body is made by the grinding of a headless carbide preform. The head is made of steel. The cross-sectional shape of the punch body may be WEDM-cut through the head. The head and punch body are joined by fillet brazing. This construction, however, raises problems. First, the two materials will often separate because the punch head is not supported by a perfectly flush substrate. Frequently, the punch head is supported by a setscrew the lower surface of which is cup-shaped. Even when the lower surface of the setscrew is ground flat, the setscrew may not provide even contact with the punch head. If the setscrew, or other support, comes in contact with the steel head but not the carbide portion of the punch, the impact of the punching operation will tend to shear the braze and separate the head and the punch body.
What is needed is a punch construction which provides the strength and rigidity of the one-piece punch construction without the cost and time problems associated therewith. What is further needed is a punch construction which provides the cost and time benefits of the common two-piece punch construction without the loss of strength and rigidity.
The present invention provides a two-piece punch construction which maintains the integrity of a one-piece punch construction while providing the cost and time advantages of a two-piece punch construction.
The present invention, in one form thereof, comprises a two-piece punch construction including a head (or head and shank combination) and a punch body. The head or head and shank combination hold the punch body and include an aperture in which the punch body is accurately located. The head or shank includes a supporting surface for the punch body. The head or head and shank are manufactured with at least one through-hole which is operable to receive a wire used in a WEDM process. The WEDM process creates the accurate aperture in the head in which the punch body is located.
An advantage of the present invention is that the punch according to the invention is less expensive than prior art punches.
Another advantage of the present invention is that the two-piece punch according to the invention is as strong and rigid as a prior art punch constructed of a single piece of material.
Yet another advantage of the present invention is that the two-piece punch according to the invention is considerably stronger than prior art two-piece punch constructions.
A still further advantage of the present invention is the reduction of production time to produce a punch according to the invention.